Method of injection moulding an undercut formation on a circular body and a closure assembly including a coupling element

ABSTRACT

A method of injection moulding an undercut formation on a circular body in which the formation is moulded in a series of arcuate sections alternating with spaces. According to the method, the moulding core, which produces the formation, is extracted by firstly relatively rotating the body and the core so that the body is expanded radially and then ejecting the body off the core. The method is applicable to the manufacture of closure members and coupling elements.

TECHNICAL FIELD

This invention relates to a method of moulding plastics articles, inparticular to produce an article comprising an undercut formation on theinner surface of a cylinder, and to a novel plastics closure member anda novel plastics coupling element comprising such an undercut formation.

BACKGROUND ART

Moulding undercut formations, for example an internal flange around acircular lid or similar closure member, or around a ring couplingelement, presents well known difficulties for injection moulding. Theflange can be moulded by the use of an appropriately recessed core, butthe radial extent of such a flange i.e. the amount of the undercut, mustbe relatively limited because of the need to extract the core from themoulding. Further, conventional techniques require the undercut to havea chamfered or sloped surface which can produce a camming action tostretch the moulding to get the flange past the mould core projectionwhich formed it.

In moulding closure members and coupling elements from plasticsmaterials, this need to have a chamfered or sloped surface can make theclosure member or coupling element less secure and less positive, whenfor example, the closure member or coupling element is required to be apress fit over a lip on the external surface of a container or matingcoupling element.

It has been proposed to produce undercut formations of the typedescribed by injection moulding using a collapsing core, but in suchcases the core leaves a so-called "witness line" on the moulded article,which is the imprint of the line between the movable parts of thecollapsing core. In the case of a closure member or coupling element,this line can appear on the internal wall above the undercut and canseverely limit the effectiveness of the seal made by the closure memberor coupling element.

The invention aims to allow deeper undercuts which moreover do not needto be sloped, and to avoid the production of witness lines. A furtherobject of the invention is to produce a novel closure member and a novelcoupling element having a deeper undercut and a more secure closureand/or sealing action.

DISCLOSURE OF INVENTION

According to one aspect the present invention provides a method ofinjection moulding an undercut formation on a circular body, whereinsaid formation is moulded in a series of arcuate sections alternatingwith spaces, and wherein the moulding core which produces the formationis extracted by firstly relatively rotating said body and said core sothat the body is expanded radially and then ejecting the body off thecore.

The invention thus provides a method for forming moulded plasticsarticle, and in particular a closure member or a coupling element,comprising an undercut formation on a circular body, said formationcomprising a series of arcuate sections alternating with spaces, aplurality of the arcuate sections each having an undercut radiallyextending surface which subtends an angle to the axis of the bodysufficient, in the case of a closure member or coupling element, to givea required degree of security to the article.

Certain closure members and coupling elements according to the inventionare novel articles and are accordingly included within the invention.

Thus in a further aspect the invention provides a moulded plasticsclosure member comprising a circular body provided with an undercutformation, said formation comprising a series of arcuate sectionsalternating with spaces, ends of the respective arcuate sections beingchamfered, the chamfered end surfaces of the arcuate sections beinglocated at an angle of less than 60° to a tangent to the circular body,and a plurality of the arcuate sections each having an undercut radiallyextending surface which is disposed at an angle to the rotational axisof the body sufficient to give a required degree of security to theclosure member.

In this aspect of the invention the moulded plastics closure memberpreferably comprises a circular body having an undercut formation and aseal on an internal wall above the undercut formation, said formationhaving a radial extent of greater than 0.005 inch (0.0125 cm) andcomprising a series of arcuate sections alternating with spaces, aplurality of the arcuate sections each having an undercut radiallyextending surface which subtends an angle to the axis of the body of atleast 80° and sufficient to give a required degree of security to theclosure member, the internal wall above the undercut formation beingdevoid of witness lines (as hereinbefore defined).

In a still further aspect, the invention also provides a couplingelement, and in particular a coupling element for use in an ostomy,incontinence, or wound care device, the element comprising an annularbody provided with an undercut formation, said formation comprising aseries of arcuate sections alternating with spaces, a plurality of theundercut arcuate sections each having a radially extending surface whichis disposed at an angle to the rotational axis of the body sufficient togive a required degree of security to the coupling element.

The undercut formation is discontinuous in a peripheral direction, butits radial extent can be greater than that achievable by conventionalmoulding techniques, and its radially extending surface can be at asteeper angle to the axis of the body. The security of such a formationas a means of engagement can be much greater than that of previouslyknown closure members and coupling elements.

The arcuate sections of the undercut formation can be of equal orunequal length, depending upon the application. Usually they will be ofequal length, but it is envisaged that, for example, a child resistclosure member may have a series of arcuate sections of unequal lengthwhich cooperate with discontinuities in a lip of a container such that,in order to open the container, the closure member needs to be rotatedrelative to the container until the arcuate sections are in registerwith the appropriate discontinuities of the lip. This position can, forexample, be indicated by aligning arrows on the closure member and thecontainer respectively.

Preferably the arcuate sections occupy as much of the periphery aspossible, although for practical reasons, and in order to facilitateremoval of the body from the core, preferably the ratio of the aggregatecircumferential length of the spaces to the aggregate circumferentiallength of the arcuate sections is at least 1:3.

The spaces themselves can be of equal or unequal length, depending uponthe application.

The radial extent of the undercut formation will depend on theapplication, and to an extent on the wall thickness of the body and thetype of plastics material employed. However a radial extent of greaterthan 0.005 inch (0.0125 cm), and up to 0,020 inch (0.051 cm) or evenmore, can be achieved using the method of the invention in appropriatecircumstances.

The radial extent of the undercut formation and the thickness andmaterial of the body need to be such as to permit relative rotation ofthe core and the body. This relative rotation causes the body to expandradially as the arcuate sections ride up on the core. To facilitate thisrelative rotation, the respective arcuate sections are chamfered and thechamfered end surfaces of the arcuate sections are not radiallydirected, but are located at an acute angle to a tangent to the circularbody. Preferably the angle is less than 60°, most preferably less than45°.

The body can, if desired be rotated with respect to the core, howeverusually, the body will be held stationary and the core rotated by anamount sufficient to cause the arcuate sections to ride up out of thedepressions in which they have been formed. The body can then easily beejected from the core by any convenient means.

In the closure member and coupling element of the invention preferablyeach of the undercut arcuate sections has a radially extending surfacewhich subtends an angle to the axis of the body sufficient to give therequired degree of security thereto. This angle will usually be at least70°, preferably 80°, and most preferably 90°. In some circumstances theangle may even exceed 90°, and extend to 95° or more, giving a slopeopposite to that necessary using conventional moulding techniques.

By the use of a steep angle of slope it is found that, in manyapplications, when the closure member or coupling element is appliedover a cooperating lip in a closure assembly, or on a mating couplingelement, an audible click can be heard, which provides the user withreassurance that the closure member or coupling element is secure. It isalso found that the greater the angle of slope the greater the securityof mating to an external lip or flange on a container, or on a matingcoupling element, particularly when that lip or flange has a radiallyextending surface which also subtends a steep angle to the axis of thebody. 90° angle external lips and flanges are readily obtainable byinjection moulding, and thus the invention provides for the first timethe opportunity to obtain a closure or coupling assembly in which boththe undercut formation on the closure member or coupling element and thelip on the component to which it is mated subtend a right angle to theaxis of the closure assembly or coupling assembly without the presenceof a witness line on an internal wall above the undercut formation.

The closure member of the invention may find application in a widevariety of products where it is necessary to form an effective sealbetween two mating parts. It is particularly useful in thosecircumstances in which the undercut formation is required on arelatively small circular body, and in those closure members in whichthe undercut formation is on the inside of an annular ring member ofU-shaped cross-section.

Thus, for example, the invention may be applied to a closure member forchild-resist containers, rendering the closure member more difficult toremove from the container as previously described. Improved securityfood containers represent a further application.

Containers to which the closure members of the present invention may beapplied are disclosed in U.S. Pat. Nos. 3,860,133, 4,434,903, 3,782,574,and 3,871,662, UK Patent Application No. GB 2096108A and French PatentNo. 2600977, and the entire disclosures of all these patents areincorporated herein by reference. It will be appreciated that hithertoin each case the manufacture of the embodiments disclosed in thesepatents will have been subject to the limitations and deficiencies ofthe prior art hereinbefore referred to.

This invention can also be embodied in a coupling element of an ostomycoupling. Such couplings are used to attach a bag for receivingdischarged material to a medical grade adhesive pad which is attached tothe wearer's peristomal skin surface.

Efforts have been made over the years to design an ostomy coupling whichremains securely attached when coupled but which can be separatedwithout causing pain to the peristomal region which is of course verytender in the days and weeks immediately following the surgicalintervention procedure.

A successful design of ostomy coupling is described and claimed inBritish Patent No. 1571657 the entire disclosure of which is alsoincorporated herein by reference. This includes a channel-sectioncoupling element which co-operates with a second coupling elementcarrying a rib of closed-loop form which is designed to inter-engagewith the channel of the first coupling element, so that a snap-fit isachieved between the two coupling elements. The channel section elementis preferably attached to the bag but may be attached instead to themedical grade adhesive pad. The second element is preferably attached tothe pad but may be attached to the bag.

It has been found that better results are obtained, in terms of securityof attachment of the two coupling elements, if certain ostensibly minorbut in fact important new features are included in the coupling devicedescribed above. Such features include the provision of an undercutformation comprising a series of arcuate sections alternating withspaces in accordance with the invention, as previously described.

According to a still further aspect of the present invention, there isprovided a ring-like coupling element of an ostomy coupling having achannel shape in cross section, defined by radially inner and outerwalls and a floor, the element being characterised in that (i) the floorof the element has a plurality of depressions therein adjacent to theinner wall, the depressions being spaced around the channel, and (ii)the radially outer wall has a plurality of inwardly-projectingshelf-like roof portions, also spaced around the channel and extendingpartly across the channel from that part of the outer wall furthest fromthe channel floor.

With this arrangement, the security of attachment of the two couplingparts is enhanced by the overlap of the roof portions and the othercoupling element; that is to say, the overlap of the roof portions tendsto prevent the second (e.g. bag side) coupling element moving out of thechannel in the axial direction of the coupling. Also, as will beunderstood from the above, the manufacture of the body side couplingelement using injection moulding techniques is facilitated. It will berealised that the present invention provides the possibility for the useof more flexible side walls for the coupling element, enabling a lowerapplication force to be used whilst providing a high degree of securityby the use of an undercut formation with a steep angle of slope relativeto the axis of the ostomy coupling element.

The invention may be applied to a wide range of plastics materials,including for example, olefin polymers and co-polymers such aspolyethylene, polypropylene, and ethylene co-polymers such asethylene-vinyl acetate co-polymers.

BRIEF DESCRIPTION OF DRAWINGS

In order that the invention may be clearly understood, exemplaryembodiments thereof will now be described with reference to theaccompanying Drawings, in which:

FIG. 1 shows a scrap sectional view of the design of a conventionalundercut lid;

FIG. 2 similarly shows a possible new design of closure member using themethod of the invention;

FIG. 3a is a sectional view of a first state in the moulding releaseprocedure according to the invention taken along line A--A in FIG. 3b;

FIG. 3b is a cross section of the mould parts in the first stage;

FIG. 3c shows an enlarged view of the circled area in FIG. 3a;

FIG. 4a is a sectional view of a second stage in the moulding releaseprocedure according to the invention taken along line A--A in FIG. 4b;

FIG. 4b is a cross section of the mould parts in the second stage;

FIG. 5a is a sectional view of a third stage in the moulding releaseprocedure according to the invention taken along line A--A in FIG. 5b;

FIG. 5b is a cross section of the mould parts in the third stage;

FIG. 6 is a plan view of one example of ostomy coupling elementaccording to the invention;

FIG. 7 is a cross-section in a radial plane on the line II--II in FIG.6;

FIG. 8 is a plan view, on an enlarged scale compared to FIG. 6, of partof the element shown in FIG. 6;

FIG. 9 is a cross-section similar to FIG. 7, but taken on the lineIII--III of FIG. 6;

FIG. 10 is a cross-sectional view, the section being on a radial planecontaining the longitudinal central axis of the coupling, and showing anostomy coupling element which is a counterpart to the element shown inFIG. 6; and

FIG. 11 is a detail view of part of the element shown in FIG. 6,illustrating an alternative shape for the undercut portion.

DETAILED DESCRIPTION OF DRAWINGS

FIG. 1 shows one edge 11 of a circular lid member 10 in section with aninwardly turned flange 12 on the edge 11. The flange 12 projects by anamount p1 and its top surface slopes downwardly at an angle a. The lidmates with an outturned flange 15 on a cylindrical body 16. Flange 15projects at right angles to the axis of the body 16.

In injection moulding the body 16, the production of flange 15 gives noproblem because the outer parts of the mould can be separate and moveapart to release the moulded article. This is not possible with theinternal core required to produce the flange 12 on lid member 10. Inthat case, the core must be forcibly pulled out and the edge 11 andflange 12 must stretch to allow this. Thus, the distance p1 isrestricted and the angle ∝ is a necessity in order that a camming actionwill occur between the mould core and the moulded article to stretch thearticle. It is apparent that lid 10 is not particularly secure on body16, since a simple pull will separate the two.

FIG. 2 shows a similar view of a moulded lid which can be produced bythe method according to the invention. Distance p2 can be greater, and ∝can be 0° or even a negative figure. With such a lid, the engagement ofthe two parts is much more secure since the mating surfaces 17, 18 ofthe flanges 12 and 15 will not allow them to separate easily.

The moulding technique is illustrated in FIGS. 3, 4 and 5 which showthree stages in the release of the moulded part, in this case anundercut ring member 20. Four mould parts are required: a cavity member21, a stripper member 22, an inner core member 23 and an outer coremember 24. The latter is the one which includes the altered mould shapewhich defines the novel undercut flange.

FIG. 3a shows the stage when injection of moulding material has beencompleted and the article is ready for ejection. The shape of the outercore member 24 is seen clearly from FIGS. 3b and 3c. The groove 25 whichforms the undercut flange 26 is discontinuous circumferentially. Thus,flange 26 is also discontinuous, but its surface 17 is not sloped. Theends 27 of the arcuate sections 28 and of the intervening spaces 29 ofthe flange 26 are however not radial but chamfered, as defined by therespective sections of groove 25. The sections 28 and the spaces 29 areof equal length.

In order to extract the moulded ring member 20, the cavity member 21 isfirst withdrawn (FIG. 4a). Then, the outer core member 24 is rotated(FIG. 4b) by the amount .O slashed. of one arcuate section 28. Thechamfered ends 27 cam outwards against the ends of the groove 25 and theflange sections 28 ride up out of the groove (FIG. 4b). The ring 20 isthen stretched outwards (FIG. 4a).

In this position, the inner and outer core member 23 and 24 can bewithdrawn downwardly, or the stripper member 22 can move upwardly, torelease the moulding (FIG. 5a), which figure also illustrates the ring20 returned to its undistorted state.

The resultant lid or collar can have a greater degree of security whenfitted to a mating member and is devoid of witness lines on the internalsealing wall 30.

It is found that because of the greater security obtained using undercutflanges having greater radial extent and steeper angle of slope withrespect to the axis of the closure member, that the lid, collar or otherclosure member can be made from a softer or thinner material making iteasier to press fit the closure member to a mating member such as alipped ring or cylinder to form a closure assembly. Notwithstanding theimproved ease of assembly, a high degree of security is maintained.

Referring now to FIGS. 6-11, these disclose the application of theinvention to an ostomy coupling. It will normally be the case that thecoupling element shown in FIG. 6 will be the bag-side element and thatshown in FIG. 10 will be the body side element, but these elements maybe reversed, that is, the FIG. 6 element may be the body side and theFIG. 10 element the bag-side, without departing from the invention.

Mutually inter-engagable coupling elements designed according to theprinciples illustrated in FIG. 6-11 may also be used as couplingelements in incontinence devices and in wound care appliances. As willbe well understood by those skilled in the ostomy art, a relatively thinpad of medical grade adhesive material is normally attached at one ofits surfaces to the skin of the wearer and at the other of its surfacesto the surface 163 shown in FIG. 10. Such a pad may have a stomalorifice therein or may have provision whereby its central portion can bepushed out or detached, so that waste material being discharged from thebody of the wearer can pass into an ostomy bag or an incontinence devicewhich is connected by the bag side coupling element 110 to the body sidecoupling element 160. Suitable materials for such an adhesive padinclude, for example, those described by Chen in U.S. Pat. No.3,339,546; by Chen et al in U.S. Pat. No. 4,192,785; by Pawelchak et alin U.S. Pat. No. 4,393080; and by Doyle et al in U.S. Pat. No.4,551,490, the entire disclosures of each of which are included hereinby reference. A particularly suitable material is that sold under theRegistered Trade Mark STOMAHESIVE by Bristol-Myers Squibb of Ickenham,Middlesex, England.

Referring firstly to FIGS. 6-9, one example of a bag side couplingelement according to the invention is illustrated. It comprises achannel section element 110 of circular form seen in FIG. 6. The femaleostomy coupling element may be normally made of a synthetic plasticsmaterial such as EVA. EVA Grade UL 00209 is one material, available fromEsso, which is suitable. The male element may be made of low densitypolyethylene.

The element 110 as seen in FIG. 6 has tabs 110A, 110B and 110C. The tabs110A and 110B are provided to facilitate attachment of a belt, and thetab 110C is provided to afford a grasping point whereby the wearer mayseparate the two coupling elements by "peeling" them apart. The couplingelement 110 has a radially outer wall 112 and a radially inner wall 114.The wall 114 surrounds a stomal orifice 118 at the centre of thecoupling. The generally ring-like or annular element 110 has a floor 116which joins the radially inner and outer walls 112, 114, this floorhaving a surface 116A to which may be attached, e.g. by adhesive, heatwelding, RF plastics welding, or other suitable method, an ostomy bagprovided with a suitable hole in one of its walls to serve as an entryfor discharges from the wearer. This entry hole is aligned with thestomal orifice 118 as is conventional in ostomy bags. The floor 116 hasa surface 116B at the base of the channel, and, into this floor, thereare provided a plurality of recesses 120. These recesses 120 in theirpresently preferred form are relatively shallow, flat bottomed, and areequally spaced peripherally around the coupling element. As seen best inFIG. 8, the recesses 120 have a shape which is approximatelyrectangular. The recesses, however, could be differently shapedaccording to the design of the moulding equipment, if desired. In apreferred embodiment of the invention, there are 24 such recesses,spaced around the ring at 15° centres. The depth of each such recess isapproximately 0.01 inch, i.e. approximately 0.254 millimetres. Theremainder of the surface 116B at the base of the channel issubstantially flat.

The recesses serve to receive one or more mould core members, forexample inner core member 23 in FIGS. 3a-5a, and serve, in extraction ofthe annular body from the mould, to prevent rotation of said bodyrelative to the said mould core member.

The radially outer wall 112 is provided with a plurality of radiallyinwardly projecting roof-like portions 130 (also referred to herein asarcuate sections) whose undersides 132 (i.e. top surfaces as seen inFIG. 7, which are undersides of the portions 130 when the femalecoupling element is laid flat on a horizontal surface) are substantiallyflat and extend substantially in a plane parallel to the planes of therespective surfaces 116A and 116B. The portion 130 extends inwardly adistance such that it covers from about 10 to about 20%, and preferablyabout 15%, of the width of the channel as will be discussed later. Inmoulding terms, the portions 130 define undercut formations. Theroof-like portions 130 may have radially inner surfaces defined byrespective continuous curves 134 that extend from the end 112B of thewall 112 in a smooth curve to merge with the surface 132. In aperipheral sense, as seen in FIGS. 6 and 8 the walls 134 curve smoothlyto merge with the radially inner surface 112A of the wall 112. Thisstructure is provided so that the portions 130 are forced outwardly byrotation of the core, as described above, so permitting the couplingelement to be readily removed from the mould.

The radially inner wall 114 is, as seen in FIG. 7, of greater heightthan the wall 112, and has its radially outer corner radiused as seen at136. In combination, the surfaces 134 and 136 contribute to the easewith which a counterpart coupling element such as is seen in FIG. 10 canbe pushed into an inter-engaged condition, relative to the couplingelement 110.

The respective roof portions 130 are equally spaced around the innerperiphery of the wall 112, and are preferably located at 45° centres.Other spacings, however, may be used. The extent in a peripheral senseof each roof portion 130 is such that it occupies an arc subtending atthe axis of revolution of the coupling element, i.e. at the centre inthe case of a geometrically circular ostomy coupling element, an angleof between 15° and 25°, preferably between about 18° and 22°. Thenumber, positioning, and angular extent of the roof portions 130 may bevaried. Preferably there are 6, 8, 10 or 12 of the roof portions, andthe roof portions are preferably equally angularly spaced in aperipheral sense around the coupling element. The roof portions 130 mayextend inwardly of the wall 112 by an amount of up to half the width ofthe channel, although preferably they extend by an amount equal to aboutone tenth to one fifth, more preferably one seventh to one fifth, and,most preferably one sixth, of the width of the channel measured in aradial direction. It has been found that this preferred amount of inwardextent, taken together with the positioning, number and arrangement ofthe roof portions, gives an ostomy coupling having a sufficient overlapof the cooperating coupling elements that the security of attachment ofthe two coupling elements against a direct pull is enhanced, but theease of separation of the two coupling elements by the "peeling method"referred to above is such that the separation can be readily achieved bymost ostomy coupling wearers, except possibly those who are very old andinfirm.

FIG. 10 illustrates, in partial cross-section, an ostomy couplingelement 160, which is also of ring-like or annular form and intended tointerfit with the element 110. In the preferred embodiment of thepresent invention, the element 160 would be the body side couplingelement. It comprises a radially extending substantially flat flange 162and a peripherally extending rib member 165 formed for mutualinter-engagement with coupling element 110. The flange 162 has a surface163 to which is secured, in any suitable manner, a pad (not shown) ofmedical grade adhesive material.

As is conventional in ostomy couplings, provision may be made on thefree surface of the medical grade adhesive pad for markings directed toassisting the user to cut out a central portion of the pad, in registrywith the stomal orifice 164. The rib member 165 has a radially outer rim167 and a radially inner flexible deflectable seal strip 168. Thepurpose of the strip 168 is to assure good sealing between the twocoupling elements when they are inter-engaged. The rim 167 has a shapedsurface 166, located at substantially 45° to the plane of the flange162. Of course other angular values may be employed but about 45° ispreferred. When the two coupling parts are connected together, the edgesof the roof portions 130 engage the surface 166 at peripherally spacedlocations. The seal strip 168 is deflected slightly radially outwardlyand bears resiliently against the surface 114A of the wall 114, soproviding a good seal and taking up any minor tolerance variations whichmay have arisen in manufacture.

In the above description, reference has been made to the surface 132 ofthe roof portion 130 being located in a plane substantially parallel tothe planes of the surfaces 116A and 116B. It is not essential to thepresent invention that the surface 132 should be planar nor that itshould be precisely parallel to the planar surfaces 116A and 116B. Aconfiguration as shown in FIG. 11 may alternatively be employed, withgood results.

Those skilled in the art of design of ostomy couplings will realise thatcertain changes and modifications may be made, without departing fromthe present invention. For example, the undercut formation could bepositioned so as to extend radially outwardly rather than inwardly andthe cooperating element would then have a radially inwardly directed ribmember co-operable therewith.

I claim:
 1. A method of injection moulding an undercut formation on asurface of a circular body wherein said formation is moulded in a seriesof arcuate sections alternating with spaces, characterised in that themoulding core which produces the formation comprises an inner coremember and an outer core member, and the core is extracted by firstlyrelatively rotating said body and said outer core member so that thebody is expanded radially by a camming action between the core and thearcuate sections and then ejecting the body off the core.
 2. The methodaccording to claim 1, characterized in that the method of moulding theundercut formation includes selecting the circular body from a closuremember or a coupling member.
 3. The method according to claim 1,characterised in that the arcuate sections of the undercut formation areof equal length.
 4. The method according to claim 1, characterised inthat the ratio of the aggregate circumferential length of the spaces tothe aggregate circumferential length of the arcuate section is at least1:3.
 5. The method according to claim 1, characterised in that thespaces are of equal length.
 6. The method according to claim 1,characterised in that the radial extent of the undercut formation isgreater than 0,005 inch (0.0125 cm).
 7. The method according to claim 1,characterised in that the ends of the respective arcuate sections arechamfered.
 8. The method according to claim 1, characterised in that thecircular body is held stationary and the core rotated by an amountsufficient to cause the arcuate sections to ride up out of thedepressions in which they have been formed.
 9. The method according toclaim 1, characterised in that each of the arcuate sections has anundercut radially extending surface which subtends an angle to the axisof the circular body of at least 80°.
 10. A moulded plastics closuremember comprising a circular body provided with a fluid passage and anundercut formation, said formation comprising a series of arcuatesections alternating with spaces, characterised in that the ends ofrespective arcuate sections are chamfered and the chamfered end surfacesof the arcuate sections are located at an angle of less than 60° to atangent to the circular body, and in that a plurality of the undercutarcuate sections each have a radially extending surface which subtendsan angle to the rotational axis of the body sufficient to give arequired degree of security to the closure member.
 11. The mouldedplastics closure member according to claim 10, characterised in that itcomprises an internal wall above the undercut formation, said formationhaving a radial extent of greater than 0,005 inch (0.0125 cm), aplurality of the undercut arcuate sections each having a radiallyextending surface which subtends an angle to the rotational axis of thebody of at least 80 degrees and sufficient to give a required degree ofsecurity to the closure member, the internal wall above the undercutformation being devoid of witness lines.
 12. The closure memberaccording to claim 10, characterised in that the arcuate sections of theundercut formation are of equal length.
 13. The closure member accordingto claim 10, characterised in that the arcuate sections of the undercutformation are of unequal length.
 14. The closure member according claim10, characterised in that the ratio of the aggregate circumferentiallength of the spaces to the aggregate circumferential length of thearcuate sections is at least 1:3.
 15. The closure member according toclaim 10, characterised in that the spaces are of equal length.
 16. Theclosure member according to claim 10, characterised in that the ends ofthe respective arcuate sections are chamfered and the chamfered endsurfaces of the arcuate sections are located at an acute angle to atangent to the circular body.
 17. The closure assembly characterised inthat it includes a closure member according to claim
 10. 18. Achild-resist container incorporating a closure assembly according toclaim 17, characterised in that the series of arcuate sections are ofunequal length which cooperate with discontinuities in a lip of thecontainer such that, in order to open the container, the closure memberneeds to be rotated relative to the container until the arcuate sectionsare in registry with the appropriate discontinuities of the lip.
 19. Thecoupling element for use in an ostomy, incontinence, or wound caredevice, the element comprising an annular body provided with an undercutformation and defining a channel for fluid communication therethrough,characterised in that said formation comprises a series of arcuatesections alternating with spaces, a plurality of the undercut arcuatesections each having a radially extending surface which subtends anangle to the axis of the body sufficient to give a required degree ofsecurity to the coupling element in respect of its attachment to acounterpart coupling element.
 20. The coupling element according toclaim 19, characterised in that said arcuate sections are equallyangularly spaced in a peripheral sense, and each occupies an arcsubtending an angle of between 25° and 15° at the axis of revolution ofthe coupling.
 21. The coupling element according to claim 19,characterised in that there are 6, 8, 10 or 12 of said arcuate sections.22. The coupling element according to claim 19, characterised in thatthe annular body comprises a channel-shaped as seen in radial section,and in which the arcuate sections extend radially inwardly from theouter wall of the channel by a distance of up to half the width of thechannel.
 23. The coupling element according to claim 22, characterisedin that the channel has a base surface comprising a plurality of shallowrecesses, serving to receive one or more mould core members.
 24. Thecoupling element according to claim 23, characterised in that therecesses serve, in extraction of the annular body from the mould, toprevent rotation of said body relative to said mould core member. 25.The coupling for use in an ostomy, wound care or incontinence device,the coupling comprising two inter-engagable coupling elements,characterised in that one coupling element is in accordance with claim19, and the other coupling element comprises an annular rib havingthereon a flexible, resilient and deflectable seal strip arranged toco-operate with a wall of the annular channel to prevent leakage ofbodily discharges.
 26. The coupling according to claim 25, characterisedin that the coupling element comprising the annular channel is thebag-side element and the rib is the body-side element.
 27. A couplingelement for use in an ostomy, incontinence, or wound care device, theelement comprising an annular body provided with an undercut formationand defining a channel for fluid communication therethrough,characterised in that said formation comprises a series of arcuatesections alternating with spaces, a plurality of the undercut arcuatesections each having a radially extending surface which subtends anangle to the rotational axis of the body sufficient to give a requireddegree of security to the device, and the radially extending surfaceextending radially inwardly or outwardly, as the case may be, by adistance such that it makes a sufficient overlap with a co-operatingcoupling element of the device so as securely to join the two couplingelements together.
 28. The coupling element according to claim 27,characterised in that the said overlap is such that the two couplingelements of the device are separable by a peeling action but not by adirect pull.
 29. A coupling element of an ostomy coupling having achannel shape in cross section, having a radial inner wall defining achannel for communication of fluid therethrough and an outer wall and afloor, the element being characterised in that (i) the floor of theelement has a plurality of depressions therein adjacent to the innerwall, the depressions being spaced around the channel, and (ii) theradially outer wall has a plurality of inwardly-projecting shelf-likeroof portions, also spaced around the channel and extending partlyacross the channel from that part of the outer wall furthest from thechannel floor.